The present invention relates generally to devices and methods for providing temporary placement of a filter in a blood vessel. More particularly, the invention provides a filter cartridge system for entrapment of embolic material in an artery or vein during an endovascular procedure. The system permits the replacement of the filter cartridge without requiring the removal of the guidewire during the endovascular procedure.
Treatment of thrombotic or atherosclerotic lesions in blood vessels using an endovascular approach has recently proven to be an effective and reliable alternative to surgical intervention in selected patients. For example, directional atherectomy and percutaneous translumenal coronary angioplasty (PTCA) with or without stent deployment are useful in treating patients with coronary occlusion. Atherectomy physically removes plaque by cutting, pulverizing, or shaving in atherosclerotic arteries using a catheter-deliverable endarterectomy device. Angioplasty enlarges the diameter of a stenotic vessel by exerting mechanical force on the vascular walls. In addition to using angioplasty, stenting, and/or atherectomy on the coronary vasculature, these endovascular techniques have also proven useful in treating other vascular lesions in, for example, carotid artery stenosis, peripheral arterial occlusive disease (especially the aorta, the iliac artery, and the femoral artery), renal artery stenosis caused by atherosclerosis or fibromuscular disease, superior vena cava syndrome, and occlusive iliac vein thrombosis resistant to thrombolysis.
It is well recognized that one of the complications associated with endovascular techniques is the dislodgment of embolic materials generated during manipulation of the vessel, thereby causing occlusion of the narrower vessels downstream and ischemia or infarct of the organ that the vessel supplies. In 1995, Waksman et al. disclosed that distal embolization is common after directional atherectomy in coronary arteries and saphenous vein grafts. See Waksman et al., American Heart Journal 129(3): 430-5 (1995), (this and all other references cited herein are expressly incorporated by reference as if fully set forth in their entirety herein). This study found that distal embolization occurs in 28% (31 out of 11) of the patients undergoing atherectomy. In Jan. 1999, Jordan, Jr. et al. disclosed that treatment of carotid stenosis using percutaneous angioplasty with stenting is associated with more than eight times the rate of microemboli seen using carotid endarterectomy. See Jordan, Jr. et al. Cardiovascular Surgery 7(1): 33-8 (1999), incorporated herein by reference. Microemboli, as detected by transcranial Doppler monitoring in this study, have been shown to be a potential cause of stroke. The embolic materials include calcium, intimal debris, atheromatous plaque, thrombi, and/or air.
There are a number of devices designed to provide blood filtering for entrapment of vascular emboli. The vast majority of these devices are designed for permanent placement in veins to prevent pulmonary embolism. A temporary venous filter device is disclosed in Bajaj, U.S. Pat. No. 5,053,008, incorporated herein by reference. The Bajaj device is an intracardiac catheter for temporary placement in the pulmonary trunk of a patient predisposed to pulmonary embolism due to, e.g., hip surgery, major trauma, major abdominal or pelvic surgery, or immobilization. The Bajaj device includes an umbrella made from meshwork that traps venous emboli before they reach the lungs. This device is designed for venous filtration and is not suitable for arterial use because of the hemodynamic differences between arteries and veins.
There are very few intravascular devices designed for arterial use. Arteries are much more flexible and elastic than veins and, in the arteries, blood flow is pulsatile with large pressure variations between systolic and diastolic flow. These pressure variations cause the artery walls to expand and contract. Blood flow rates in the arteries vary from about 0.1 to 5 L/min. Ginsburg, U.S. Pat. No. 4,873,978, discloses an arterial filtering system, which includes a catheter with a strainer device at its distal end. This device is inserted into the vessel downstream from the treatment site and, after treatment, the strainer is collapsed around the entrapped emboli and removed from the body. The Ginsburg device, however, is integral with the catheter, unlike the devices described later herein. Ing. Walter Hengst GmbH and Co, German Patent DE 34 17 738, discloses another arterial filter having a folding linkage system that converts the filter from the collapsed to the expanded state.
Filters mounted to the distal end of guidewires have been proposed for intravascular blood filtration. A majority of these devices include a filter that is attached to a guidewire and is mechanically actuated via struts or a pre-shaped basket that deploys in the vessel. These filters are typically mesh xe2x80x9cparachutesxe2x80x9d that are attached to the shaft of the wire at the distal end and to wire struts that extend outward in a radial direction at their proximal end. The radial struts open the proximal end of the filter to the wall of the vessel. Blood flowing through the vessel is forced through the mesh thereby capturing embolic material in the filter.
Gilson et al., International Publication No. WO 99/23976 describes a guidewire with a filter slideably mounted thereon. Although the filter is not fixed to the guidewire at a single point, the filter is limited in its range of movement by two stops at the distal end of the guidewire, the stops being relatively closely spaced. Thus, unlike the present invention, in Gilson et al. the filter cannot be removed unless the entire guidewire is removed.
The useful in vivo time of a guidewire filter will vary, depending upon the type of procedure, the patient, and the blood flow. These factors may contribute to relatively short use time because of, for example, blood coagulation or excessive emboli clogging the filter mesh. Because for existing devices, the guidewire and the filter are integrated into one inseparable device, changing the filter after its useful in vivo deployment time has been completed requires the removal and replacement of the guidewire. This change requires time consuming and costly fluoroscopic guidance to reposition the new guidewire and filter.
There is a need in the art for a device that will not require removal and replacement of the guidewire should the in vivo useful life of a blood filter be exceeded. The present invention addresses that need by providing a blood cartridge filter that may be used and replaced without requiring the removal of the guidewire.
The present invention provides devices and methods for directing a blood filter into position using a guidewire wherein the blood filter may be deployed and replaced independently of the guidewire. More specifically, a guidewire cartridge filter system is disclosed for capturing embolic material generated during a surgical procedure within a region of interest in an artery or vein.
In accordance with the present invention, the cartridge filter system comprises an elongate member that acts as an advancing mechanism, e.g., a push wire or sheath, having a distal region attached to a filter, e.g., a parachute, basket, or scroll filter. In certain embodiments, the filter may be releasably attached to the elongate member through an interlock, which may comprise, for example, a mechanical interlock or electromechanical interlock. The filter may comprise an expansion frame and a filter material, typically a filter mesh, attached to the expansion frame. The cartridge filter system includes means for engaging the guidewire, such as a wire guide that slideably engages a guidewire. The wire guide may be attached to either or both of the elongate member and the filter. In certain embodiments, the wire guide comprises a ring having an aperture adapted to receive the guidewire. In certain other embodiments, the wire guide comprises a body portion of the elongate member having a longitudinally extending groove adapted to slideably engage the guidewire. The body portion may thus have a C-shaped cross section. Because the wire guide slideably engages the guidewire, the filter may be directed into place by the guidewire, but deployed and retracted independently of the guidewire. The filter can be placed in a collapsed condition to facilitate entry into a vessel and an expanded condition to capture embolic material in the vessel. As used herein, xe2x80x9cadvancing mechanismxe2x80x9d denotes any elongate member or structure suitable for advancing the filter into position within a vessel while engaging the guidewire through the wire guide. The elongate member could thus be either a wire or a catheter wherein the lumen of the catheter serves as the wire guide. In one embodiment, the elongate member comprises a sheath wherein the lumen of the sheath serves as the wire guide.
Filters suitable for use within the filter system of the present invention are described, for example, in U.S. Pat. No. 5,910,154, incorporated herein by reference in its entirety. In one embodiment, the filter is biased to automatically open radially within a blood vessel. In such filters, the expansion frame may comprise a plurality of struts or arms attached to and extending distally from a distal end of the elongate member. The struts are connected to each other at each end and have an intermediate region that is biased to expand radially. Filter mesh is attached typically between the intermediate region such as the midpoint and the distal ends of the struts, thereby defining a substantially hemispherical or conical shaped filter assembly. In embodiments of the invention wherein the elongate member comprises a sheath, a filter biased to automatically open radially may be releasably carried in its collapsed condition within the sheath wherein a mechanical interlock between elongate member and the filter is formed by the friction between the filter and the lumenal wall of the sheath.
Other filters suitable for the present invention are not biased to automatically open radially within a blood vessel. In such filters, the elongate member may comprise a sheath containing an inner wire, and the expansion frame includes a plurality of struts attached to the distal end of the sheath. The struts extend distally from the sheath and attach to the distal end of the inner wire that is exposed distally beyond the sheath. At an intermediate region, the struts are notched or otherwise biased to fold out radially. Filter mesh is attached to the struts between the intermediate region and the distal end of the inner wire. With the sheath fixed, the inner wire is proximally displaced, compressing the struts and causing them to bend or buckle at the intermediate region and move radially outwardly, expanding the filter mesh across the blood vessel. As used herein, xe2x80x9cinner wirexe2x80x9d means any structure suitable to be slideably disposed within the sheath and stiff enough to compress the struts as the inner wire is proximally displaced with respect to the sheath. The inner wire may thus comprise an inner sheath within which the guidewire is slideably disposed.
In certain other embodiments, the filter may comprise a fluid operated filter wherein the expansion frame includes a balloon that inflates to expand the filter into an enlarged condition for use. The construction and use of expansion frames and associated filter mesh have been thoroughly discussed in earlier applications including Barbut et al., U.S. application Ser. No. 08/533,137, filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut et al., U.S. Pat. No. 5,769,816, Barbut et al., U.S. application Ser. No. 08/645,762, filed May 14, 1996, and Barbut et al., U.S. Pat. No. 5,662,671, and the contents of each of these prior applications are expressly incorporated herein by reference.
The methods of the present invention include prevention of distal embolization during an endovascular procedure to remove emboli and/or foreign bodies such as gas bubbles from blood vessels. The vessels include the coronary artery, aorta, common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, basilar artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, posterior tibial artery, and all other arteries carrying oxygenated blood. Suitable venous vessels include the superior vena cava, inferior vena cava, external and internal jugular veins, brachiocephalic vein, pulmonary artery, subclavian vein, brachial vein, axillary vein, iliac vein, renal vein, femoral vein, profunda femoris vein, great saphenous vein, portal vein, splenic vein, hepatic vein, and azygous vein.
In a method of using the cartridge filter system, the distal end of the guidewire is inserted through an artery or vein and advanced into or beyond a region of interest, typically a stenotic lesion caused by buildup of atherosclerotic plaque and/or thrombi. The guidewire may be inserted percutaneously, laparoscopically, or through an open surgical incision. In a collapsed condition, the filter and the elongate member are advanced over the guidewire, having the wire guide of the filter cartridge system engaging the guidewire. In one embodiment, the wire guide engages the elongate member at a single discrete location in a monorail fashion such as through a ring structure. If the wire guide includes a body portion of the elongate member having a longitudinally extending groove adapted to slideably engage the guidewire, the body portion engages the guidewire in an over-the-wire fashion wherein the guidewire is slideably disposed within the groove of the body portion. Alternatively, the elongate member may comprise a sheath wherein the guidewire is slideably disposed within the lumen of the sheath in an over-the-wire fashion such that the lumen serves as the wire guide. Regardless of whether the wire guide engages the guidewire in a monorail or an over-the-wire fashion, the filter is then expanded downstream of the vascular occlusion. If the wire guide engages the guidewire in an over-the-wire fashion, the elongate member may be left in the vessel during the in vivo deployment time of the filter because the elongate member and the guidewire are then integrated into a single unit, limiting the interference with further deployment of therapy devices in the vessel. If, however, the wire guide engages the guidewire in a monorail fashion, the elongate member is preferably removed from the filter during the in vivo deployment time of the filter to prevent a clinician from having to contend with the dependent movement of both the guidewire and the elongate member during the surgical procedure. Preferably, in such embodiments, the elongate member releasably attaches to the filter through a mechanical interlock. After deploying the filter, the mechanical interlock is released to allow the removal of the elongate member.
Should the in vivo deployment time of the filter be exceeded, the used filter is retracted from the body and the guidewire. If the filter and elongate member were separated by releasing an interlock, the wire guide on the elongate member must be engaged with the guidewire so that the elongate member may be displaced distally on the guidewire towards the used filter. The interlock would then be re-engaged to connect the elongate member and the used filter together whereupon the elongate member may be retracted to remove the used filter. If the elongate member and the used filter were permanently attached, the elongate member may simply be retracted to remove the used filter. An additional filter and elongate member may then be advanced over the guidewire as described herein. Because the present invention allows the removal and replacement of filters without require the removal of the guidewire, the filter system may be denoted a xe2x80x9ccartridge filterxe2x80x9d system in that the filter is akin to, for example, a printer cartridge, readily replaceable within the printer. After the stenotic lesion is removed or otherwise treated and an adequate lumenal diameter is established, the filter is collapsed and removed, together with the captured embolic debris, from the vessel by withdrawing another elongate member used for retrieval. Alternatively, the filter could be removed by withdrawing the guidewire to remove the entire filter system.